CD38 is a human lymphocyte differentiation antigen and multifunctional surface receptor with both enzymatic and cell adhesion functions. Ligation of CD38 with agonistic antibodies induces diverse effects in hematopoietic cells. As an enzyme CD38 synthesizes cADPR from NAD and hydrolyzes cADPR to ADPR. The existence of a transmembrane cell surface glycoprotein, which is both a receptor and an enzyme, presents an intriguing and as yet unanswered question: What is the function of this ectozyme? In B-cells CD38 functions as a co-receptor for BCR signaling. CD38 may also mediate ADP ribosylation of cell surface proteins as well as regulating insulin secretion and interacting with CD31 and the CD3/TCR complex. A structural investigation of CD38 is essential to understand the immunological significance of this multifunctional molecule. We seek time on BL 9-1/7-1 in order to collect high-resolution native data and heavy atom derivative data sets for initial structure determination and to subsequently elucidate the catalytic mechanism. A previous test done on BL 7-1 with a tiny crystal resulted in diffraction to almost 2.8 E. Beam time on BL 9-1/7-1 is requested in order to attain a high resolution structure to comprehend the reaction mechanism of CD38.